Corrosion Inhibition and Adsorption Properties of <i>Commelina benghalensis</i> Leaves Extract on Mild Steel in 1M H<sub>2</sub>SO<sub>4</sub> Solution

Abstract

The corrosion inhibition of mild steel in 1M sulphuric acid solution by the ethanol extract of Commelina benghalensis (C. B) leaves was determined using gravimetric technique. Phytochemical analysis was carried out on the extract and the effect of extract concentration, temperature, immersion time and acid concentration on the corrosion process was determined. The corrosion inhibition efficiency of the extract increased with increase in the concentration of the extract and decreased with increase in temperature. Increase in temperature also increased the corrosion rate of mild steel in 1M sulphuric acid in the absence and presence of different concentrations of the extract. The adsorption of the plant extract obeyed Langmuir and Freundlich adsorption isotherms. The process of physical adsorption was proposed for the extract from the trends of inhibition efficiency with temperature and from calculated values of Gibbs free energy, activation energy and enthalpy of adsorption. Gibbs free energy values for the reactions were less than 20kJ/mol, indicating physical adsorption process and were also found to be negative, indicating that the adsorption process was spontaneous. The corrosion inhibition efficiency (% IE) of the plant extract was attributed to the phytochemical constituents (alkaloids, flavonoids, tannins, saponins, phenolics, steroids and cardiac glycosides) present in them. The results showed that Commelina benghalensis can serve as a good corrosion inhibitor of mild steel in acid medium, since it reached a corrosion inhibition efficiency (% IE) of 91.91% at 2.0g/L extract concentration.

Experimental Study on Adsorption and Corrosion Inhibition Properties of <i>Urena lobata</i> Leaves Extract on Mild Steel in Acidic Medium

“…This may be attributed to the protective ability of the leave extract. Similar findings have been reported by Odidika et al [12].…”

“…The results show that the weight loss increased with increase in extract concentration. The more the interaction between the compounds present in the extract the more the protection of the coupons, Odidika et al [12] reported similar observation.…”